How is steel strength measured?

Question

My gf's brother is trying to convince me that these knives he got are stronger than a samurai sword. He says the sword is a 10 and the knife is a 52. He doesn't know what units they are being measured in and neither do I. Is steel like gold karats where the lower the number the stronger the metal?

Answer 1

He might be talking about hardness.   Not related to gold karats.

http://en.wikipedia.org/wiki/Rockwell_ha...

The hardness of steel is related to it's ability to hold an edge, but excessive hardness in a sword would be a disadvantage, as the sword would be more likely to break.

I have never had the opportunity to closely examine a samurai sword, but I have seen very old and contemporary damascus steel blades,and they are beautiful as well as functional.  

Grandpa

Answer 2

This might be ksi, or thousand pounds per square inch. This indicates at which stress level the knife will yield. To understand this, say you have a steel rod that is one square inch in cross-sectional area. It could hold up 52000 pounds for a 52ksi steel.

Most structural steels are around 30 ksi steels, a samurai sword is probably up there with that.  I believe the Samurai sword represents humans first use of steel and they really did master the craft.  Maybe the knife is not steel or a tungsten steel?

This may be in some other units too, but that's the basic idea.

Answer 3

Regular steel is measured in Pascals (Pa). Usually the value is large so MegaPascals (MPa) that is one millions pascals.

Answer 4

I'd believe that a samurai sword is lower in tensile strenght, no big deal since the samurai sword is 1000 years old and they didn't have the ability to make high straight steel.

Furthermore, high strenght steel tend to be brittle, ie they shatter if hit to hard, so a sword needs to be able to bend a little without breaking.